The immune system defends the body against viruses, microorganisms, cancer cells, and foreign proteins. It is composed of cells and organs that work together. The lymphoid system includes lymphoid cells like T cells and B cells that originate and mature in primary lymphoid organs like the thymus and bone marrow. Secondary lymphoid organs, such as lymph nodes and the spleen, help activate immune cells and filter pathogens from lymph and blood. Together, these cells and organs recognize and eliminate threats to the body.

1. Cells and organs of immune system
Cells and organs of immune system
Presented by
Yogesh kumar
[M.sc. Bioinformatics 1st sem]
Bioinformatics]

2. The immune system is an organization of molecules,
cells, tissues, and organ with specialized role in
defending against viruses, microorganisms, cancer
cells, and nonself proteins.
The cells involved in the immune reaction are
organized into tissue and organs which are
collectively refer as lymphoid system. This system
perform the major function of protecting the body
against the various microorganisms that enter the
body through all the possible routes. It is formed of
lymphoid cells and lymphoid organs.

5. Figure 24-4: Cells of the immune system

6. They have specific name in the body as depending on their location

8. T cell B cells
. Originate from bone marrow . Originate and mature in
and mature in thymus bone marrow
. They can’t function without . They can functions due to
MHC molecules presence of antibody
. They are differentiate into TH . They are not
and Tc
. They have CD8 markers . They have CD4 markers
. They secrete cytokines . They do lysis of the virus-infected cell

11. Primary lymphoid organs..are the major site of
lymphopoiesis . Here the lymphoid stem cells proliferate,
differentiate and mature into immunocompetent cells in the
absence of antigenic stimulation. The Thymus and the bursa of
fabricius (in birds) are the primary lymphoid organs.
THYMUS
 Blobbed Organ on Top of Heart
 Reaches Max. Size During Puberty in 10 year of age
› 70g infants, 3 g in adults
 95-99% Of T Cells Die in Thymus
› self reactivity or no reactivity to Ag
 Consists of Cortex and Medulla

12. In birds, undifferentiated lymphocytes move
from the bone
marrow to the bursa of Fabricius where B
cells mature. In mammals,
the bone marrow is the site of B-cell
maturation. Like
thymic selection during T-cell maturation, a
selection process
within the bone marrow eliminates B cells
with self-reactive antibody
receptors (the acquisition of tolerance).

13. The secondary lymphoid organs include the well
organized, encapsulated spleen and lymph nodes.
The spleen is the larger secondary lymphoid organ
located in the abdominal cavity. where lymph
node specialize for trapping micro organism and
antigens from local tissues, the spleen specializes in
filtering the blood and trapping blood borne
microorganism and antigens. once trapped by
macrophage and dendritic cells, the pathogen is
phagocytosed and antigens are presented to b
and T cells, which become activated to carry out
their immune functions.

15. Lymph node..lies at the junction of
lymphatic vessels where they filter out
harmful microorganism and antigen from
the lymph pathogens and antigens are
trapped by phagocytic and dendritic
cells. Fixed macrophages and then
phagocyte the foreign material. It is with
in lymph node that B cells proliferate into
antibody secreting plasma cells

20. THANK
YOU